256 Q. II Darwin— Stresses cau*nl !■„ thr Earth hij 



F.B.S.* 



The existence of dry land proves that the earth's surface is 

 not a figure of equilibrium appropriate for the diurnal rotation. 

 Hence the interior of the earth must, be in a state of stress, 

 and as the land docs not sink in, nor the sea-bed rise up, the 

 materials of which the earth is made must be strong enough to 



We are thus led to inquire how the stresses are distributed 

 in the earth's mass, and what are their magnitudes. These 

 points cannot be discussed without an hypothesis as to the 

 interior constitution of the earth. 



In this paper I have solved a problem of the kind 

 for the case of a homogeneous incompressible elastic sphere, 



applied the results to the case of the i 



be urged that the earth is not such as this 



The view which was formerly generally held was that the 

 earth consists of a solid crust floating on a molten nucleus. It 

 has also been lately maintained by Dr. August Ritter, in a 

 series of interesting paper.-, that the interior of the earth is gas- 

 eous, f A third opinion, contended i'nv by Sir William Thom- 

 son, and of which I am myself an adherent, is that the earth is 

 throughout a solid of great rigidity; he explains the flow of 

 lava from volcanoes either by the existence of liquid vesicles 

 in the interior, or by the melting of solid matter, existing at 

 high temperature and pressure, at points where diminution of 

 pressure occurs. 



There is another consideration, which is consistent with Sir 

 William Thomson's view, and which was pointed out to me by 



